The Richardsonian Romanesque building was designed by George Keller, executed by Shepley, Rutan and Coolidge and built in 1889.

To the west is a triangular parking lot and the viaduct carrying Interstate 84 and U.S. Route 6, which curves around the north of the station as well.

It is a three-story rectangular building in rough-faced Portland brownstone with two smaller, similarly shaped two-story wings on the north and south.

The main building has a flat roof; the wings are gabled and tiled, with dormer windows piercing them at regular intervals.

[3] On the east (front) facade, a wide set of steps rises to the main entrance, beneath a flat hood at the springlines of three of the large segmental arches that run across the first story.

The second track and platform were removed by Amtrak in the 1990s to reduce maintenance costs and because the underlying structure is no longer strong enough to support more than one train at a time.

A 260-foot (79 m) section of the platform was converted to high level for accessible boarding as part of the Hartford Line project.

The I-84 Hartford Project may require realigning the highway and rail line, in which case new platforms would be constructed on the new alignment, though Union Station would continue to be used for ticketing and waiting area.

[8] In November 2024, ConnDOT was awarded a $2.6 million federal grant for planning of the station relocation and associated double-tracking work.